Distillation of



tate the meet-sewn nciulpmen t,

Patented July 22, 1952 .7 I .HAL'O-OLEFINS I 'Alan C. Nixon, Berkeley, Calif., assignor to Shell Development Company, San Francisco, Calif.,- 1 1 a corporation-of Delaware w t o! the invention relates to the separation or methallyl mamas ifon'i isocrotyl chloride.

in thelzprrodution t! "2-allzenyl halides on a practical seam, an example, 'by halcgenation of an rilenn erw denydwnalogenauon or a d-ihalo a11- "hyzirocarbon, ithe resulting product is mwn umvamamy e'ifntami-natedwi th other haloolel'lns :genemny-rccmprlsmg l alkenyl halides. In the practical scale production of methallyl chloride this nompcuhd is generally obtained in adnimture with-varying amou nts ef 'isocrctyl chloride. The emu-w iitill-i a "2 -"alkef1y'l halide as starting or riritermediatematerial' in the production of derivative products tlsiereffi6m';isoften depen' centmion' the absence' tnerein or any subanioimt nr other haloscleflns. The pre en'cexict such contaminant nhe-mefinsta n n lers exeeediirgiy tlimcuit "the prctmction ofsatisiact'ory yields of derivative products amenable to murmur ism-mention Without additional relatively costly steps armament Further: -disadi antages occasioned mymerprie eme er t cont mam: halc-oieflnifi the I2 al1 eny1 halide include operational *difiicirlties attfibutable to side rea tions'iand maeaseumruswenessr Often these undesirablaeflects for "the contaminant are increased iii izthe presence :or other materials em- .plcyed in subsequent use or treatment of the z-alkenyl halide. 'fiiieh difiiculties or hecesfias, or exam le, apparatus iccnrstructeu of material par tifiifl'aTflyRsistaiit to co'nrosl'on therebymaterially increasing the initial installation cost or the unit wherein each lialo olefin contaminated 2 alkeny1 halideisto beprocessed; ,3 v I V e obtaining 701" "a =2=alkeiiyl halide which is ce of any substantial.- amount of contaminant Wo d made P ticularly-dimr halide; thereby-gentle as separation by ides "is a 'tertiary' carbcn atom. fA particular Serial No. 129,700

-. l Glaims. (o1. 2o2-42 flifilication November 26, 1 949;; I

such methods 'as jpracticfal -'scale fractionating means diflicult if notfimp'o'ssible.

It is an object of the present invention to provide an improved process enabling the more enicient. separation of; 2- alkenyl halides ,irom the corresponding I-alkenyl, halides, havi-ng 1 closely approximating boiling temperatures. '2 p 3 Another object oitheinyention is-the-pro- 7 vision of an improved process enabling the more efilcient separation of halo olefin mixtures consisting essentially of 2-alkenyl halides in admixture with l-alkenyli halidesl'zwhich have"; closely approximatingboiling temperatures and iniwhich halides the unsaturated-carbon atom in the position adjacent to thellialogenat'edcarbon atom is a tertiary carbon atom. I

A more particiilar of the invention is the provision or an mproved fprocess enabling the more efficient separation ojfa 2 alkenyl halide from a mixture consisting essentially of 2-alkenyl halides and l -"alkenyl halides having four-carbon atoms to the" molecule an'd wherein the-unsaturated carbon atom in the position adij acentt'o the halogenated carbcnxatmh is afltertiarycarbOnatom. I a 5 Y A still more particular object offtheinvntion is the provision of an improved process enabling the more efiicient separation of methallyl chloride from a mixture ofghaIo-olefins containing said methallyl chloride in admixture with .iso-

crotylrchloride Other objects and advantages of the invention will become appar t" r'o'm the fol; lowing detailed'description-therofl I In accordance with the invention a *2 llienyl halide is separated from a halo-olefin mixture consisting essentially of said 2-alkenyl halide in admixture with a ;1-'all4enyl halide the boiling temperature of which closely approximates that. of the 2 -alken yl halide, ydis ill n t eimix ure alkenyl halide: Y I

The invention is applied-to the separaticnef of which the present invention, is directed, comprises the grouping whereinX represents a halogen. Representative examples of such Z-alkenyl halides comprise:

The l-alkenyl halides, also referred to as vinyltype halides having from three to nine carbon atoms to the molecule which are separated from the above-defined 2-alkenyl halides in the process of the invention comprise the grouping The process of the invention is applied with particular advantage to the separation of the 2- alkenyl halides wherein the unsaturated carbon atom adjacent to the halogenated carbon atom is a tertiary carbon atom, that is, those comprising the grouping 1 r; from the corresponding l-alkenyl halides having closely approximating boiling temperature and containing the grouping Examples urine members' of this sub-class of 2-alkeny1 halides comprise CHz=C(CH3)CH2C1, CHFC (CH3) CHZBI, CH2=C (CH3) CH2]:

cwm pckcrmcmorfetc. -Examples of the members or the corresponding sub-class of 1- alkenyl halides comprise: CH3C(CHa)==CHC1 The process of the invention is particularly effective in serving as a means for the separation of the Z-alkenyl halides having four carbon atoms to the molecule from the corresponding l-alkenyl halides having boiling temperatures closely approximating those of the corresponding 2 -alkenyl halides. Mixtures of suchf'four carbon atom alkenyl halides separated in accordance with the invention comprise, for example, mixtures of methallyl chloride with isocrotyl chloride, methallyl bromide with isocrotyl bromide, etc.

In the alkenyl halides described hereinabove, to the separation .of which the present invention is directed, the-halogen atom can be, for example, chlorine, bromine or iodine.

The invention is, however, applied, with particular advantage to the separation of the above defined alkenyl halides wherein the halogen atom is a halogen having an atomic number of from 1'7 to 35, inclusive. By the phrase consisting essentially of as used throughout the specification and attached claims it is intended to mean that the compositions to which it is' applied arem'ade up' almost entirely of the components recited 'andthat these components are the main andjcharacterizingones; but this expression .does .notexclude the presence of minor amounts of other constituentswhich are ordinarily found to bepresent in such compositions. i The ketones,'in the presence of whichthe alkenyl halides are .distilled 'in accordance with the process of the invention, consist ofthe aliphatic saturated ketones the boiling; temperatures of which are lower than, :or do not substantially exceed those of, the alkenyl halidesbeing separated. The particular. ketone chosen for a particularseparation will depend uponthe-specific mixture being separated." In a preferred method of carrying out the invention-the alkenyl halide mixture to be separated is distilled in the presence of analiphatic' saturated ketone the boiling-temperature of which lies between that of the 2-alkenyl halide component of the. mixture and a temperature about -20 below this temperature. Examples of aliphatic ketones which may be em ployed in the process of the invention comprise,

for example, 'acetoneu 1 In the distillation of the alkenyl halide mixtures in accordance'with'the process-of the invention the alkenyl halide mixture to be separated and the aliphatic. ketone are introduced into. a suitabledistillation zone and therein subjected to distillation. The aliphatic ketone may be added to the alkenyl halide mixture prior to its introductioninto the distillation zone or a part or all of the ketone maybeintroduced as a'separate streaminto thedistillation zone. Any conventional typeof distillation apparatus may be em ployed, the distillation may be executed in batch, semi-continuous or continuous operation; The distillationm'ay be carried out at subatmospheric, atmospheric or superatmospheric pressure.

The distillation will-proceed with the formation of a minimum boiling azeotrope containing l-alkenyl halide component of the alkenyl halide mixture and theadded k'etonef The" l alkenyl halide will thus'be taken overhead in the distillation leaving the 2-alkeny1 halide as residual or bottoms product; The amount of aliphatic ketone added to the r alkenyl"halide chargemay vary within the scope of the invention depending upon the compositionfof the specific halide mixture charged, the distillation conditions employed, and

residual alkenyl halide product, desired; Ingen;

eral, it has been fundadvantageous to add the I by weight of isocrotyl chloride. The-"isocr y sets-ass necessary to form "a minimum "boiling ia zeotrope with the .l-alkenyl halide component, although greater "or lesser amounts of the ketone may be employed within the scope of the invention. Thus, in the separation of "zalkenyl from l alkenyi halides having four cai'bon 'atoinsto the molecule, such as the separation of "isocrotyl chloride from methallyl chloridm'with the aid of acetone at atmospheric .pressure, it has been .fouridfthat the azeotrope formed contains 19% chloride -fac'tone 'azectrqpejthus Icbtain v boiling temperature or 551.6". ,C. .at atni'os er ic pressure. By continuous distillation iffa typlate column at a re'iiux'to "feedlratio o:f -.3,'j -with a 2:3 acetone ftoftdt'al fclilorid H "ratio, reduction of the isocrotyl chloride content in a methallyl chloride-isocrotyl chloride :mixture; from 13% to 2% by weighthas been obtainedwith a99% frecovery of'methallylchloride. when completere moval of the isocrotyl chloride 'fromthe methallyl chloride is desired, the acetone is added in an amount at least equal to four times the weight of isocrotyl chloride in the mixture being distilled. In a preferred method of purifying the methallyl chloride contaminated with isocrotyl chloride, however, the mixture is distilled in the presence of an amount of acetone at least equal to ten times the weight of the isocrotyl chloride content of the methallyl chloride-isocrotyl chloride charge. The invention is of coure not limited with respect to the amount of acetone added in excess of the minimum required amount. Thus the use of amounts ranging from four to 50, and preferably from four to times the weight of isocrotyl chloride content of the mixture is employed. Greater amounts of the aliphatic ketone may, however, be employed within the scope of the invention.

Separation of the aliphatic ketone from admixture with the l-alkenyl halide as obtained overhead from the distillation may be accomplished by conventional means comprising such steps as, for example, solvent extraction, extractive distillation, selective adsorption, etc. Thus, acetone may be recovered from the mixtures of acetone-isocrotyl chloride obtained overhead in the distillation of methallyl chlorideisocrotyl chloride mixtures in the presence of acetone by subjecting the mixture to one or more such steps as scrubbing with water, extractive distillation in the presence of water, etc. In the continuous operation of the process of the invention, aliphatic ketone recovered from the distillation products may be recycled to the distillation zone wherein the mixture of Z-alkenyl halides and l-alkenyl halides are being distilled in accordance with the invention.

The efficiency with which 2-alkenyl halides are separated from mixtures comprising them in admixture with l-alkenyl halides in accordance with the method of the invention is illustrated by the following examples:

EXAIVIPLE I Methallyl chloride contaminated by the presence therein of isocrotyl chloride in an amount of 13% by weight was subjected to batch distillation in the presence of added acetone. Addition of the acetone to the methallyl chloride-isocrotyl chloride mixture resulted in a composite charge having the following composition in weight per cent:

KaboutT8O ;of the" a1 isocrotylrchloride conrnwm1 t w saw was imme chloridein the charge was in ith'e distillate.

we: 'centiby wei tm'aticnunaer mitten tantially liide'ritical I mi c s -Y with the iexceptio e distillation wa gqenducted at'a pressure or 400 mm. 'A'ft'er distilling oif 41.3% of the charge it was found that approximately 89 of the isocrotyl chloride content of the original charge had been taken overhead and that the distillate contained less than 2.2% methallyl chloride.

EXAMPLE III Isocrotyl chloride was removed from admixture with methallyl chloride by continuous azeotropic distillation in a fractionating column in the presence of acetone. The acetone was added to the methallyl chloride-isocrotyl chloride mixture before introduction into the distillation I column. Conditions employed and results obtained in each of three operations are indicated in the following table:

Table A42, B11, B12, Run 1 2 3 Plates in column 40 40 40 20 20 20 Reflux to feed ratio 3. 3 6. 8 6. 4 Feed, weight per cent:

acetone 33. P. 40. 0 40. 0

methallyl chloride. 60. 0 53. 0 53.0

isocrotyl chloride. 6. 7 7. O 7. 0 Overhead product, weight per cent 37 49 46 acetone 86. 2 81. 0 86. 8

methallyl chloride. 3.0 5. 9 2. 4

isocrotyl chloride. 10.8 13. 1 10. 8 Bottom product, weight per cent 63 51 54 acetone 2. 1 0. 2 0. 3

methallyl chloride 96. 7 98. 3 98. 1

isocrotyl chloride 1. l 1. 5 1. 6

The invention claimed is:

1. The process for separating methallyl chloride from a mixture of alkenyl chlorides consisting essentially of methallyl chloride and isocrotyl chloride, which comprises the step of distilling said mixture in the presence of an amount of acetone at least equal to four times the weight of the isocrotyl chloride content of said mixture.

2. The process for separating methallyl chloride from a mixture of alkenyl chlorides consisting essentially of methallyl chloride and isocrotyl chloride, which comprises the step of distilling said mixture in the presence of an amount of acetone in the'range of from about 4 to about 25 times the weight of the isocrotyl chloride content of said mixture.

3. The process for purifying methallyl chloride contaminated by the presence therein of impurities consisting essentially of isocrotyl chloride, which comprises the step of distilling said con- :epn ined in the overtaminated methallyl chloride in the presence of an amount of acetone substantially exceeding the weight of the isocrotyl chloride content of said contaminated methallyl chloride. 7

v 4., Theprocess for purifying a z -alkenyl chloride, haying four carbon atoms to the molec ule contaminated 'bythe presence therein of a 1 alkenyl chloride the boiling temperature of which closely approximatesthat of said 2-alkenyl chloride which comprises the step of distilling said contaminated 2-alkenyl chloride in'the presence of an amount of acetone substantially exceeding the weight of 'l-alkenyl chloride in said contaminated 2-alkenyl chloride.

5. The process for purifying a 2-alkenyl chloride having four carbon atoms to the molecule contaminated by the presence therein of a 1- alkenyl chloride the boiling temperature of which closely approximates that of said 2-alkenylchloride which comprises the step of distilling said contaminated 2.-alkenyl'chloride in the presence of an amount of acetone in the range of from about-four to about twenty-five .times the weight of 1,-alken'y1. chloride in said contaminated alkenyl chloride. a

ALANC NIXON.

. g REFERENCES CITED The following references are of record in the f le of this patent:

' I UNITED STATES PATENTS No. 11, November 1939, pages 1413-1419, Halogenation of Hydrocarbons, by Burgin et a]. 

4. THE PROCESS FOR PURIFYING A 2-ALKENYL CHLORIDE HAVINNG FOUR CARBON ATOMS TO THE MOLECULE CONTAMINATED BY THE PRESENCE THEREIN OF A 1ALKENYL CHLORIDE THE BOILING TEMPERATURE OF WHICH CLOSELY APPROXIMATES THAT OF SAID 2-ALKENYL CHLORIDE WHICH COMPRISES THE STEP OF DISTILLING SAID CONTAMINATED 2-ALKENYL CHLORIDE IN THE PRESENCE OF AN AMOUNT OF ACETONE SUBSTANTIAALLY EXCEEDING THE WEIGHT OF 1-ALKENYL CHLORIDE IN SAID CONTAMINATED 2-ALKENYL CHLORIDE, 